/*******************************************************************************
 * Copyright (c) 2014-2015 IBM Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *	IBM Zurich Research Lab - initial API, implementation and documentation
 *******************************************************************************/

//! \file
#include "lmic.h"

#if !defined(MINRX_SYMS)
	#define MINRX_SYMS 5
#endif // !defined(MINRX_SYMS)

#define PAMBL_SYMS 8
#define PAMBL_FSK	5
#define PRERX_FSK	1
#define RXLEN_FSK	(1+5+2)

#define BCN_INTV_osticks		sec2osticks(BCN_INTV_sec)
#define TXRX_GUARD_osticks		ms2osticks(TXRX_GUARD_ms)
#define JOIN_GUARD_osticks		ms2osticks(JOIN_GUARD_ms)
#define DELAY_DNW1_osticks		sec2osticks(DELAY_DNW1)
#define DELAY_DNW2_osticks		sec2osticks(DELAY_DNW2)
#define DELAY_JACC1_osticks		sec2osticks(DELAY_JACC1)
#define DELAY_JACC2_osticks		sec2osticks(DELAY_JACC2)
#define DELAY_EXTDNW2_osticks	sec2osticks(DELAY_EXTDNW2)
#define BCN_RESERVE_osticks		ms2osticks(BCN_RESERVE_ms)
#define BCN_GUARD_osticks		ms2osticks(BCN_GUARD_ms)
#define BCN_WINDOW_osticks		ms2osticks(BCN_WINDOW_ms)
#define AIRTIME_BCN_osticks		us2osticks(AIRTIME_BCN)

#if defined(CFG_eu868)
	#define DNW2_SAFETY_ZONE	ms2osticks(3000)
#endif
#if defined(CFG_us915)
	#define DNW2_SAFETY_ZONE	ms2osticks(750)
#endif

// Special APIs - for development or testing
#define isTESTMODE() 0

DEFINE_LMIC;
DECL_ON_LMIC_EVENT;


// Fwd decls.
static void engineUpdate(void);
static void startScan (void);


// ================================================================================
// BEG OS - default implementations for certain OS suport functions

#if !defined(HAS_os_calls)

#if !defined(os_rlsbf2)
uint16_t os_rlsbf2 (const uint8_t * buf) {
	return (uint16_t)(buf[0] | (buf[1]<<8));
}
#endif

#if !defined(os_rlsbf4)
uint32_t os_rlsbf4 (const uint8_t * buf) {
	return (uint32_t)(buf[0] | (buf[1]<<8) | ((uint32_t)buf[2]<<16) | ((uint32_t)buf[3]<<24));
}
#endif


#if !defined(os_rmsbf4)
uint32_t os_rmsbf4 (const uint8_t * buf) {
	return (uint32_t)(buf[3] | (buf[2]<<8) | ((uint32_t)buf[1]<<16) | ((uint32_t)buf[0]<<24));
}
#endif


#if !defined(os_wlsbf2)
void os_wlsbf2 (uint8_t * buf, uint16_t v) {
	buf[0] = v;
	buf[1] = v>>8;
}
#endif

#if !defined(os_wlsbf4)
void os_wlsbf4 (uint8_t * buf, uint32_t v) {
	buf[0] = v;
	buf[1] = v>>8;
	buf[2] = v>>16;
	buf[3] = v>>24;
}
#endif

#if !defined(os_wmsbf4)
void os_wmsbf4 (uint8_t * buf, uint32_t v) {
	buf[3] = v;
	buf[2] = v>>8;
	buf[1] = v>>16;
	buf[0] = v>>24;
}
#endif

#if !defined(os_getBattLevel)
uint8_t os_getBattLevel (void) {
	return MCMD_DEVS_BATT_NOINFO;
}
#endif

#if !defined(os_crc16)
// New CRC-16 CCITT(XMODEM) checksum for beacons:
uint16_t os_crc16 (uint8_t * data, uint len) {
	uint16_t remainder = 0;
	uint16_t polynomial = 0x1021;
	for ( uint i = 0; i < len; i++ ) {
		remainder ^= data[i] << 8;
		for ( uint8_t bit = 8; bit > 0; bit--) {
			if ( (remainder & 0x8000) )
				remainder = (remainder << 1) ^ polynomial;
			else 
				remainder <<= 1;
		}
	}
	return remainder;
}
#endif

#endif // !HAS_os_calls

// END OS - default implementations for certain OS suport functions
// ================================================================================

// ================================================================================
// BEG AES

static void micB0 (uint32_t devaddr, uint32_t seqno, int dndir, int len) {
	os_clearMem(AESaux,16);
	AESaux[0]	= 0x49;
	AESaux[5]	= dndir?1:0;
	AESaux[15] = len;
	os_wlsbf4(AESaux+ 6,devaddr);
	os_wlsbf4(AESaux+10,seqno);
}


static int aes_verifyMic (const uint8_t * key, uint32_t devaddr, uint32_t seqno, int dndir, uint8_t * pdu, int len) {
	micB0(devaddr, seqno, dndir, len);
	os_copyMem(AESkey,key,16);
	return os_aes(AES_MIC, pdu, len) == os_rmsbf4(pdu+len);
}


static void aes_appendMic (const uint8_t * key, uint32_t devaddr, uint32_t seqno, int dndir, uint8_t * pdu, int len) {
	micB0(devaddr, seqno, dndir, len);
	os_copyMem(AESkey,key,16);
	// MSB because of internal structure of AES
	os_wmsbf4(pdu+len, os_aes(AES_MIC, pdu, len));
}


static void aes_appendMic0 (uint8_t * pdu, int len) {
	os_getDevKey(AESkey);
	os_wmsbf4(pdu+len, os_aes(AES_MIC|AES_MICNOAUX, pdu, len));	// MSB because of internal structure of AES
}


static int aes_verifyMic0 (uint8_t * pdu, int len) {
	os_getDevKey(AESkey);
	return os_aes(AES_MIC|AES_MICNOAUX, pdu, len) == os_rmsbf4(pdu+len);
}


static void aes_encrypt (uint8_t * pdu, int len) {
	os_getDevKey(AESkey);
	os_aes(AES_ENC, pdu, len);
}


static void aes_cipher (const uint8_t * key, uint32_t devaddr, uint32_t seqno, int dndir, uint8_t * payload, int len) {
	if ( len <= 0 )
		return;
	os_clearMem(AESaux, 16);
	AESaux[0] = AESaux[15] = 1; // mode=cipher / dir=down / block counter=1
	AESaux[5] = dndir?1:0;
	os_wlsbf4(AESaux+ 6,devaddr);
	os_wlsbf4(AESaux+10,seqno);
	os_copyMem(AESkey,key,16);
	os_aes(AES_CTR, payload, len);
}


static void aes_sessKeys (uint16_t devnonce, const uint8_t * artnonce, uint8_t * nwkkey, uint8_t * artkey) {
	os_clearMem(nwkkey, 16);
	nwkkey[0] = 0x01;
	os_copyMem(nwkkey+1, artnonce, LEN_ARTNONCE+LEN_NETID);
	os_wlsbf2(nwkkey+1+LEN_ARTNONCE+LEN_NETID, devnonce);
	os_copyMem(artkey, nwkkey, 16);
	artkey[0] = 0x02;

	os_getDevKey(AESkey);
	os_aes(AES_ENC, nwkkey, 16);
	os_getDevKey(AESkey);
	os_aes(AES_ENC, artkey, 16);
}

// END AES
// ================================================================================


// ================================================================================
// BEG LORA

#if defined(CFG_eu868) // ========================================

#define maxFrameLen(dr) ((dr)<=DR_SF9 ? maxFrameLens[(dr)] : 0xFF)
const uint8_t maxFrameLens [] = { 64,64,64,123 };

const uint8_t _DR2RPS_CRC[] = {
	ILLEGAL_RPS,
	(uint8_t)MAKERPS(SF12, BW125, CR_4_5, 0, 0),
	(uint8_t)MAKERPS(SF11, BW125, CR_4_5, 0, 0),
	(uint8_t)MAKERPS(SF10, BW125, CR_4_5, 0, 0),
	(uint8_t)MAKERPS(SF9,	BW125, CR_4_5, 0, 0),
	(uint8_t)MAKERPS(SF8,	BW125, CR_4_5, 0, 0),
	(uint8_t)MAKERPS(SF7,	BW125, CR_4_5, 0, 0),
	(uint8_t)MAKERPS(SF7,	BW250, CR_4_5, 0, 0),
	(uint8_t)MAKERPS(FSK,	BW125, CR_4_5, 0, 0),
	ILLEGAL_RPS
};

static const int8_t TXPOWLEVELS[] = {
	20, 14, 11, 8, 5, 2, 0,0, 0,0,0,0, 0,0,0,0
};
#define pow2dBm(mcmd_ladr_p1) (TXPOWLEVELS[(mcmd_ladr_p1&MCMD_LADR_POW_MASK)>>MCMD_LADR_POW_SHIFT])

#elif defined(CFG_us915) // ========================================

#define maxFrameLen(dr) ((dr)<=DR_SF11CR ? maxFrameLens[(dr)] : 0xFF)
const uint8_t maxFrameLens [] = { 24,66,142,255,255,255,255,255,	66,142 };

const uint8_t _DR2RPS_CRC[] = {
	ILLEGAL_RPS,
	MAKERPS(SF10, BW125, CR_4_5, 0, 0),
	MAKERPS(SF9 , BW125, CR_4_5, 0, 0),
	MAKERPS(SF8 , BW125, CR_4_5, 0, 0),
	MAKERPS(SF7 , BW125, CR_4_5, 0, 0),
	MAKERPS(SF8 , BW500, CR_4_5, 0, 0),
	ILLEGAL_RPS ,
	ILLEGAL_RPS ,
	ILLEGAL_RPS ,
	MAKERPS(SF12, BW500, CR_4_5, 0, 0),
	MAKERPS(SF11, BW500, CR_4_5, 0, 0),
	MAKERPS(SF10, BW500, CR_4_5, 0, 0),
	MAKERPS(SF9 , BW500, CR_4_5, 0, 0),
	MAKERPS(SF8 , BW500, CR_4_5, 0, 0),
	MAKERPS(SF7 , BW500, CR_4_5, 0, 0),
	ILLEGAL_RPS
};

#define pow2dBm(mcmd_ladr_p1) ((int8_t)(30 - (((mcmd_ladr_p1)&MCMD_LADR_POW_MASK)<<1)))

#endif // ================================================

static const uint8_t SENSITIVITY[7][3] = {
	// ------------bw----------
	// 125kHz	250kHz	500kHz
	{ 141-109,	141-109, 141-109 },	// FSK
	{ 141-127,	141-124, 141-121 },	// SF7
	{ 141-129,	141-126, 141-123 },	// SF8
	{ 141-132,	141-129, 141-126 },	// SF9
	{ 141-135,	141-132, 141-129 },	// SF10
	{ 141-138,	141-135, 141-132 },	// SF11
	{ 141-141,	141-138, 141-135 }	// SF12
};

int getSensitivity (uint16_t rps) {
	return -141 + SENSITIVITY[getSf(rps)][getBw(rps)];
}

ostime_t calcAirTime (uint16_t rps, uint8_t plen) {
	uint8_t bw = getBw(rps);	// 0,1,2 = 125,250,500kHz
	uint8_t sf = getSf(rps);	// 0=FSK, 1..6 = SF7..12
	if ( sf == FSK ) {
		return (plen+/*preamble*/5+/*syncword*/3+/*len*/1+/*crc*/2) * /*bits/byte*/8
			* (int32_t)OSTICKS_PER_SEC / /*kbit/s*/50000;
	}
	uint8_t sfx = 4*(sf+(7-SF7));
	uint8_t q = sfx - (sf >= SF11 ? 8 : 0);
	int tmp = 8*plen - sfx + 28 + (getNocrc(rps)?0:16) - (getIh(rps)?20:0);
	if ( tmp > 0 ) {
		tmp = (tmp + q - 1) / q;
		tmp *= getCr(rps)+5;
		tmp += 8;
	} else {
		tmp = 8;
	}
	tmp = (tmp<<2) + /*preamble*/49 /* 4 * (8 + 4.25) */;
	// bw = 125000 = 15625 * 2^3
	//		250000 = 15625 * 2^4
	//		500000 = 15625 * 2^5
	// sf = 7..12
	//
	// osticks =	tmp * OSTICKS_PER_SEC * 1<<sf / bw
	//
	// 3 => counter reduced divisor 125000/8 => 15625
	// 2 => counter 2 shift on tmp
	sfx = sf+(7-SF7) - (3+2) - bw;
	int div = 15625;
	if ( sfx > 4 ) {
		// prevent 32bit signed int overflow in last step
		div >>= sfx-4;
		sfx = 4;
	}
	// Need 32bit arithmetic for this last step
	return (((ostime_t)tmp << sfx) * OSTICKS_PER_SEC + div/2) / div;
}

extern inline uint16_t updr2rps (uint8_t dr);
extern inline uint16_t dndr2rps (uint8_t dr);
extern inline int isFasterDR (uint8_t dr1, uint8_t dr2);
extern inline int isSlowerDR (uint8_t dr1, uint8_t dr2);
extern inline uint8_t	incDR	(uint8_t dr);
extern inline uint8_t	decDR	(uint8_t dr);
extern inline uint8_t	assertDR (uint8_t dr);
extern inline uint8_t	validDR	(uint8_t dr);
extern inline uint8_t	lowerDR	(uint8_t dr, uint8_t n);

extern inline uint8_t	getSf	(uint16_t params);
extern inline uint16_t setSf	(uint16_t params, uint8_t sf);
extern inline uint8_t	getBw	(uint16_t params);
extern inline uint16_t setBw	(uint16_t params, uint8_t cr);
extern inline uint8_t	getCr	(uint16_t params);
extern inline uint16_t setCr	(uint16_t params, uint8_t cr);
extern inline int	getNocrc (uint16_t params);
extern inline uint16_t setNocrc (uint16_t params, int nocrc);
extern inline int	getIh	(uint16_t params);
extern inline uint16_t setIh	(uint16_t params, int ih);
extern inline uint16_t makeRps	(uint8_t sf, uint8_t bw, uint8_t cr, int ih, int nocrc);
extern inline int	sameSfBw (uint16_t r1, uint16_t r2);

// END LORA
// ================================================================================


// Adjust DR for TX retries
//	- indexed by retry count
//	- return steps to lower DR
static const uint8_t DRADJUST[2+TXCONF_ATTEMPTS] = {
	// normal frames - 1st try / no retry
	0,
	// confirmed frames
	0,0,1,0,1,0,1,0,0
};


// Table below defines the size of one symbol as
//	symtime = 256us * 2^T(sf,bw)
// 256us is called one symunit. 
//				 SF:									
//		BW:		|__7___8___9__10__11__12
//		125kHz	|	2	3	4	5	6	7
//		250kHz	|	1	2	3	4	5	6
//		500kHz	|	0	1	2	3	4	5
//	
// Times for half symbol per DR
// Per DR table to minimize rounding errors
static const ostime_t DR2HSYM_osticks[] = {
#if defined(CFG_eu868)
#define dr2hsym(dr) (DR2HSYM_osticks[(dr)])
	us2osticksRound(128<<7),	// DR_SF12
	us2osticksRound(128<<6),	// DR_SF11
	us2osticksRound(128<<5),	// DR_SF10
	us2osticksRound(128<<4),	// DR_SF9
	us2osticksRound(128<<3),	// DR_SF8
	us2osticksRound(128<<2),	// DR_SF7
	us2osticksRound(128<<1),	// DR_SF7B
	us2osticksRound(80)		// FSK -- not used (time for 1/2 byte)
#elif defined(CFG_us915)
#define dr2hsym(dr) (DR2HSYM_osticks[(dr)&7])	// map DR_SFnCR -> 0-6
	us2osticksRound(128<<5),	// DR_SF10	DR_SF12CR
	us2osticksRound(128<<4),	// DR_SF9	DR_SF11CR
	us2osticksRound(128<<3),	// DR_SF8	DR_SF10CR
	us2osticksRound(128<<2),	// DR_SF7	DR_SF9CR
	us2osticksRound(128<<1),	// DR_SF8C	DR_SF8CR
	us2osticksRound(128<<0)	// ------	DR_SF7CR
#endif
};


static ostime_t calcRxWindow (uint8_t secs, uint8_t dr) {
	ostime_t rxoff, err;
	if ( secs==0 ) {
		// aka 128 secs (next becaon)
		rxoff = LMIC.drift;
		err = LMIC.lastDriftDiff;
	} else {
		// scheduled RX window within secs into current beacon period
		rxoff = (LMIC.drift * (ostime_t)secs) >> BCN_INTV_exp;
		err = (LMIC.lastDriftDiff * (ostime_t)secs) >> BCN_INTV_exp;
	}
	uint8_t rxsyms = MINRX_SYMS;
	err += (ostime_t)LMIC.maxDriftDiff * LMIC.missedBcns;
	LMIC.rxsyms = MINRX_SYMS + (err / dr2hsym(dr));

	return (rxsyms-PAMBL_SYMS) * dr2hsym(dr) + rxoff;
}


// Setup beacon RX parameters assuming we have an error of ms (aka +/-(ms/2))
static void calcBcnRxWindowFromMillis (uint8_t ms, bool ini) {
	if ( ini ) {
		LMIC.drift = 0;
		LMIC.maxDriftDiff = 0;
		LMIC.missedBcns = 0;
		LMIC.bcninfo.flags |= BCN_NODRIFT|BCN_NODDIFF;
	}
	ostime_t hsym = dr2hsym(DR_BCN);
	LMIC.bcnRxsyms = MINRX_SYMS + ms2osticksCeil(ms) / hsym;
	LMIC.bcnRxtime = LMIC.bcninfo.txtime + BCN_INTV_osticks - (LMIC.bcnRxsyms-PAMBL_SYMS) * hsym;
}


// Setup scheduled RX window (ping/multicast slot)
static void rxschedInit (rxsched_t * rxsched)
{
	os_clearMem(AESkey,16);
	os_clearMem(LMIC.frame+8,8);
	os_wlsbf4(LMIC.frame, LMIC.bcninfo.time);
	os_wlsbf4(LMIC.frame+4, LMIC.devaddr);
	os_aes(AES_ENC,LMIC.frame,16);
	uint8_t intvExp = rxsched->intvExp;
	ostime_t off = os_rlsbf2(LMIC.frame) & (0x0FFF >> (7 - intvExp)); // random offset (slot units)
	rxsched->rxbase = (LMIC.bcninfo.txtime +
						BCN_RESERVE_osticks +
						ms2osticks(BCN_SLOT_SPAN_ms * off)); // random offset osticks
	rxsched->slot	= 0;
	rxsched->rxtime = rxsched->rxbase - calcRxWindow(/*secs BCN_RESERVE*/2+(1<<intvExp),rxsched->dr);
	rxsched->rxsyms = LMIC.rxsyms;
}

static bool rxschedNext (rxsched_t * rxsched, ostime_t cando)
{
	for(;;)
	{
		if ( rxsched->rxtime - cando >= 0 )
			return 1;
		uint8_t slot;
		if ( (slot = rxsched->slot) >= 128 )
			return 0;
		uint8_t intv = 1 << rxsched->intvExp;
		if ( (rxsched->slot = (slot += (intv))) >= 128 )
			return 0;
		rxsched->rxtime = rxsched->rxbase
			+ ((BCN_WINDOW_osticks * (ostime_t)slot) >> BCN_INTV_exp)
			- calcRxWindow(/*secs BCN_RESERVE*/ 2 + slot + intv, rxsched->dr);
		rxsched->rxsyms = LMIC.rxsyms;
	}
}

static ostime_t rndDelay (uint8_t secSpan)
{
	uint16_t r = os_getRndU2();
	ostime_t delay = r;
	if ( delay > OSTICKS_PER_SEC )
		delay = r % (uint16_t)OSTICKS_PER_SEC;
	if ( secSpan > 0 )
		delay += ((uint8_t)r % secSpan) * OSTICKS_PER_SEC;
	return delay;
}


static void txDelay (ostime_t reftime, uint8_t secSpan) {
	reftime += rndDelay(secSpan);
	if ( LMIC.globalDutyRate == 0	||	(reftime - LMIC.globalDutyAvail) > 0 ) {
		LMIC.globalDutyAvail = reftime;
		LMIC.opmode |= OP_RNDTX;
	}
}


static void setDrJoin (uint8_t reason, uint8_t dr) {
	EV(drChange, INFO, (e_.reason	= reason,
						e_.deveui	= MAIN::CDEV->getEui(),
						e_.dr		= dr|DR_PAGE,
						e_.txpow	 = LMIC.adrTxPow,
						e_.prevdr	= LMIC.datarate|DR_PAGE,
						e_.prevtxpow = LMIC.adrTxPow));
	LMIC.datarate = dr;
	DO_DEVDB(LMIC.datarate,datarate);
}


static void setDrTxpow (uint8_t reason, uint8_t dr, int8_t pow) {
	EV(drChange, INFO, (e_.reason	= reason,
						e_.deveui	= MAIN::CDEV->getEui(),
						e_.dr		= dr|DR_PAGE,
						e_.txpow	 = pow,
						e_.prevdr	= LMIC.datarate|DR_PAGE,
						e_.prevtxpow = LMIC.adrTxPow));
	
	if ( pow != KEEP_TXPOW )
		LMIC.adrTxPow = pow;
	if ( LMIC.datarate != dr ) {
		LMIC.datarate = dr;
		DO_DEVDB(LMIC.datarate,datarate);
		LMIC.opmode |= OP_NEXTCHNL;
	}
}


void LMIC_stopPingable (void) {
	LMIC.opmode &= ~(OP_PINGABLE|OP_PINGINI);
}


void LMIC_setPingable (uint8_t intvExp) {
	// Change setting
	LMIC.ping.intvExp = (intvExp & 0x7);
	LMIC.opmode |= OP_PINGABLE;
	// App may call LMIC_enableTracking() explicitely before
	// Otherwise tracking is implicitly enabled here
	if ( (LMIC.opmode & (OP_TRACK|OP_SCAN)) == 0	&&	LMIC.bcninfoTries == 0 )
		LMIC_enableTracking(0);
}


#if defined(CFG_eu868)
// ================================================================================
//
// BEG: EU868 related stuff
//
enum { NUM_DEFAULT_CHANNELS=6 };
static const uint32_t iniChannelFreq[12] = {
	// Join frequencies and duty cycle limit (0.1%)
	EU868_F1|BAND_MILLI, EU868_J4|BAND_MILLI,
	EU868_F2|BAND_MILLI, EU868_J5|BAND_MILLI,
	EU868_F3|BAND_MILLI, EU868_J6|BAND_MILLI,
	// Default operational frequencies
	EU868_F1|BAND_CENTI, EU868_F2|BAND_CENTI, EU868_F3|BAND_CENTI,
	EU868_F4|BAND_MILLI, EU868_F5|BAND_MILLI, EU868_F6|BAND_DECI
};

static void initDefaultChannels (bool join) {
	os_clearMem(&LMIC.channelFreq, sizeof(LMIC.channelFreq));
	os_clearMem(&LMIC.channelDrMap, sizeof(LMIC.channelDrMap));
	os_clearMem(&LMIC.bands, sizeof(LMIC.bands));

	LMIC.channelMap = 0x3F;
	uint8_t su = join ? 0 : 6;
	for ( uint8_t fu=0; fu<6; fu++,su++ ) {
		LMIC.channelFreq[fu]	= iniChannelFreq[su];
		LMIC.channelDrMap[fu] = DR_RANGE_MAP(DR_SF12,DR_SF7);
	}
	if ( !join ) {
		LMIC.channelDrMap[5] = DR_RANGE_MAP(DR_SF12,DR_SF7);
		LMIC.channelDrMap[1] = DR_RANGE_MAP(DR_SF12,DR_FSK);
	}

	LMIC.bands[BAND_MILLI].txcap	= 1000;	// 0.1%
	LMIC.bands[BAND_MILLI].txpow	= 14;
	LMIC.bands[BAND_MILLI].lastchnl = os_getRndU1() % MAX_CHANNELS;
	LMIC.bands[BAND_CENTI].txcap	= 100;	// 1%
	LMIC.bands[BAND_CENTI].txpow	= 14;
	LMIC.bands[BAND_CENTI].lastchnl = os_getRndU1() % MAX_CHANNELS;
	LMIC.bands[BAND_DECI ].txcap	= 10;	// 10%
	LMIC.bands[BAND_DECI ].txpow	= 27;
	LMIC.bands[BAND_CENTI].lastchnl = os_getRndU1() % MAX_CHANNELS;
	LMIC.bands[BAND_MILLI].avail = 
	LMIC.bands[BAND_CENTI].avail =
	LMIC.bands[BAND_DECI ].avail = os_getTime();
}

bool LMIC_setupBand (uint8_t bandidx, int8_t txpow, uint16_t txcap) {
	if ( bandidx > BAND_AUX ) return 0;
	band_t* b = &LMIC.bands[bandidx];
	b->txpow = txpow;
	b->txcap = txcap;
	b->avail = os_getTime();
	b->lastchnl = os_getRndU1() % MAX_CHANNELS;
	return 1;
}

bool LMIC_setupChannel (uint8_t chidx, uint32_t freq, uint16_t drmap, int8_t band) {
	if ( chidx >= MAX_CHANNELS )
		return 0;
	if ( band == -1 ) {
		if ( freq >= 869400000 && freq <= 869650000 )
			freq |= BAND_DECI;	// 10% 27dBm
		else if ( (freq >= 868000000 && freq <= 868600000) ||
				 (freq >= 869700000 && freq <= 870000000)	)
			freq |= BAND_CENTI;	// 1% 14dBm 
		else 
			freq |= BAND_MILLI;	// 0.1% 14dBm
	} else {
		if ( band > BAND_AUX ) return 0;
		freq = (freq&~3) | band;
	}
	LMIC.channelFreq [chidx] = freq;
	LMIC.channelDrMap[chidx] = drmap==0 ? DR_RANGE_MAP(DR_SF12,DR_SF7) : drmap;
	LMIC.channelMap |= 1<<chidx;	// enabled right away
	return 1;
}

void LMIC_disableChannel (uint8_t channel)
{
	LMIC.channelFreq[channel] = 0;
	LMIC.channelDrMap[channel] = 0;
	LMIC.channelMap &= ~(1<<channel);
}

static uint32_t convFreq (uint8_t * ptr) {
	uint32_t freq = (os_rlsbf4(ptr-1) >> 8) * 100;
	if ( freq < EU868_FREQ_MIN || freq > EU868_FREQ_MAX )
		freq = 0;
	return freq;
}

static uint8_t mapChannels (uint8_t chpage, uint16_t chmap)
{
	// Bad page, disable all channel, enable non-existent
	if ( chpage != 0 || chmap==0 || (chmap & ~LMIC.channelMap) != 0 )
		return 0;	// illegal input
	for ( uint8_t chnl=0; chnl<MAX_CHANNELS; chnl++ )
	{
		if ( (chmap & (1<<chnl)) != 0 && LMIC.channelFreq[chnl] == 0 )
			chmap &= ~(1<<chnl); // ignore - channel is not defined
	}
	LMIC.channelMap = chmap;
	return 1;
}


static void updateTx (ostime_t txbeg)
{
	uint32_t freq = LMIC.channelFreq[LMIC.txChnl];
	// Update global/band specific duty cycle stats
	ostime_t airtime = calcAirTime(LMIC.rps, LMIC.dataLen);
	// Update channel/global duty cycle stats
	band_t * band = &LMIC.bands[freq & 0x3];
	LMIC.freq	= freq & ~(uint32_t)3;
	LMIC.txpow = band->txpow;
	band->avail = txbeg + airtime * band->txcap;
	if ( LMIC.globalDutyRate != 0 )
		LMIC.globalDutyAvail = txbeg + (airtime<<LMIC.globalDutyRate);
}

static ostime_t nextTx (ostime_t now)
{
	uint8_t bmap = 0xF;
	do
	{
		ostime_t mintime = now + /*10h*/36000 * OSTICKS_PER_SEC;
		uint8_t band = 0;
		for ( uint8_t bi = 0; bi < 4; bi++ )
			if ( (bmap & (1 << bi)) && mintime - LMIC.bands[bi].avail > 0 )
				mintime = LMIC.bands[band = bi].avail;

		// Find next channel in given band
		uint8_t chnl = LMIC.bands[band].lastchnl;
		for ( uint8_t ci=0; ci<MAX_CHANNELS; ci++ )
		{
			if ( (chnl = (chnl+1)) >= MAX_CHANNELS )
				chnl -=	MAX_CHANNELS;
			if ((LMIC.channelMap & (1 << chnl)) != 0	// channel enabled
			&&	(LMIC.channelDrMap[chnl] & (1<<(LMIC.datarate&0xF))) != 0
			&&	band == (LMIC.channelFreq[chnl] & 0x3)
				)
			{ // in selected band
				LMIC.txChnl = LMIC.bands[band].lastchnl = chnl;
				return mintime;
			}
		}
		if ( (bmap &= ~(1<<band)) == 0 )
		{	// No feasible channel	found!
			return mintime;
		}
	} while (1);
}


static void setBcnRxParams (void)
{
	LMIC.dataLen = 0;
	LMIC.freq = LMIC.channelFreq[LMIC.bcnChnl] & ~(uint32_t)3;
	LMIC.rps	= setIh(setNocrc(dndr2rps((uint8_t)DR_BCN),1),LEN_BCN);
}

#define setRx1Params() /*LMIC.freq/rps remain unchanged*/

static void initJoinLoop (void)
{
	LMIC.txChnl = os_getRndU1() % 6;
	LMIC.adrTxPow = 14;
	setDrJoin(DRCHG_SET, DR_SF7);
	initDefaultChannels(1);
	ASSERT((LMIC.opmode & OP_NEXTCHNL) == 0);
	LMIC.txend = LMIC.bands[BAND_MILLI].avail + rndDelay(8);
}


static ostime_t nextJoinState (void)
{
	uint8_t failed = 0;

	// Try 869.x and then 864.x with same DR
	// If both fail try next lower datarate
	if ( ++LMIC.txChnl == 6 )
		LMIC.txChnl = 0;
	if ( (++LMIC.txCnt & 1) == 0 ) {
		// Lower DR every 2nd try (having tried 868.x and 864.x with the same DR)
		if ( LMIC.datarate == DR_SF12 )
			failed = 1; // we have tried all DR - signal EV_JOIN_FAILED
		else
			setDrJoin(DRCHG_NOJACC, decDR((uint8_t)LMIC.datarate));
	}
	// Clear NEXTCHNL because join state engine controls channel hopping
	LMIC.opmode &= ~OP_NEXTCHNL;
	// Move txend to randomize synchronized concurrent joins.
	// Duty cycle is based on txend.
	ostime_t time = os_getTime();
	if ( time - LMIC.bands[BAND_MILLI].avail < 0 )
		time = LMIC.bands[BAND_MILLI].avail;
	LMIC.txend = time +
		(isTESTMODE()
		 // Avoid collision with JOIN ACCEPT @ SF12 being sent by GW (but we missed it)
		 ? DNW2_SAFETY_ZONE
		 // Otherwise: randomize join (street lamp case):
		 // SF12:255, SF11:127, .., SF7:8secs
		 : DNW2_SAFETY_ZONE+rndDelay(255>>LMIC.datarate));
	// 1 - triggers EV_JOIN_FAILED event
	return failed;
}

//
// END: EU868 related stuff
//
// ================================================================================
#elif defined(CFG_us915)
// ================================================================================
//
// BEG: US915 related stuff
//


static void initDefaultChannels (void) {
	for ( uint8_t i=0; i<4; i++ )
		LMIC.channelMap[i] = 0xFFFF;
	LMIC.channelMap[4] = 0x00FF;
}

static uint32_t convFreq (uint8_t * ptr) {
	uint32_t freq = (os_rlsbf4(ptr-1) >> 8) * 100;
	if ( freq < US915_FREQ_MIN || freq > US915_FREQ_MAX )
		freq = 0;
	return freq;
}

bool LMIC_setupChannel (uint8_t chidx, uint32_t freq, uint16_t drmap, int8_t band) {
	if ( chidx < 72 || chidx >= 72+MAX_XCHANNELS )
		return 0; // channels 0..71 are hardwired
	chidx -= 72;
	LMIC.xchFreq[chidx] = freq;
	LMIC.xchDrMap[chidx] = drmap==0 ? DR_RANGE_MAP(DR_SF10,DR_SF8C) : drmap;
	LMIC.channelMap[chidx>>4] |= (1<<(chidx&0xF));
	return 1;
}

void LMIC_disableChannel (uint8_t channel) {
	if ( channel < 72+MAX_XCHANNELS )
		LMIC.channelMap[channel/4] &= ~(1<<(channel&0xF));
}

static uint8_t mapChannels (uint8_t chpage, uint16_t chmap)
{
	if ( chpage == MCMD_LADR_CHP_125ON || chpage == MCMD_LADR_CHP_125OFF )
	{
		uint16_t en125 = chpage == MCMD_LADR_CHP_125ON ? 0xFFFF : 0x0000;
		for ( uint8_t u = 0; u < 4; u++ )
			LMIC.channelMap[u] = en125;
		LMIC.channelMap[64 / 16] = chmap;
	}
	else
	{
		if ( chpage >= (72 + MAX_XCHANNELS + 15) / 16 )
			return 0;
		LMIC.channelMap[chpage] = chmap;
	}
	return 1;
}

static void updateTx (ostime_t txbeg)
{
	uint8_t chnl = LMIC.txChnl;
	if ( chnl < 64 )
	{
		LMIC.freq = US915_125kHz_UPFBASE + chnl*US915_125kHz_UPFSTEP;
		LMIC.txpow = 30;
		return;
	}
	LMIC.txpow = 26;
	if ( chnl < 64+8 )
	{
		LMIC.freq = US915_500kHz_UPFBASE + (chnl-64) * US915_500kHz_UPFSTEP;
	}
	else
	{
		ASSERT(chnl < 64+8+MAX_XCHANNELS);
		LMIC.freq = LMIC.xchFreq[chnl-72];
	}

	// Update global duty cycle stats
	if ( LMIC.globalDutyRate != 0 )
	{
		ostime_t airtime = calcAirTime(LMIC.rps, LMIC.dataLen);
		LMIC.globalDutyAvail = txbeg + (airtime<<LMIC.globalDutyRate);
	}
}

// US does not have duty cycling - return now as earliest TX time
#define nextTx(now) (_nextTx(),(now))

static void _nextTx (void)
{
	if ( LMIC.chRnd ==0 )
		LMIC.chRnd = os_getRndU1() & 0x3F;
	if ( LMIC.datarate >= DR_SF8C )
	{	// 500kHz
		uint8_t map = LMIC.channelMap[64 / 16] & 0xFF;
		for ( uint8_t i = 0; i < 8; i++ )
		{
			if ( (map & (1 << (++LMIC.chRnd & 7))) != 0 )
			{
				LMIC.txChnl = 64 + (LMIC.chRnd & 7);
				return;
			}
		}
	}
	else
	{	// 125kHz
		for ( uint8_t i=0; i<64; i++ )
		{
			uint8_t chnl = ++LMIC.chRnd & 0x3F;
			if ( (LMIC.channelMap[(chnl >> 4)] & (1 << (chnl & 0xF))) != 0 )
			{
				LMIC.txChnl = chnl;
				return;
			}
		}
	}
	// No feasible channel	found! Keep old one.
}

static void setBcnRxParams (void)
{
	LMIC.dataLen = 0;
	LMIC.freq = US915_500kHz_DNFBASE + LMIC.bcnChnl * US915_500kHz_DNFSTEP;
	LMIC.rps  = setIh(setNocrc(dndr2rps((uint8_t)DR_BCN), 1), LEN_BCN);
}

#define setRx1Params()	\
	{												\
		LMIC.freq = US915_500kHz_DNFBASE + (LMIC.txChnl & 0x7) * US915_500kHz_DNFSTEP;	\
		if ( /* TX datarate */LMIC.dndr < DR_SF8C )	\
			LMIC.dndr += DR_SF10CR - DR_SF10;		\
		else if ( LMIC.dndr == DR_SF8C )			\
			LMIC.dndr = DR_SF7CR;					\
		LMIC.rps = dndr2rps(LMIC.dndr);				\
	}

static void initJoinLoop (void)
{
	LMIC.chRnd = 0;
	LMIC.txChnl = 0;
	LMIC.adrTxPow = 20;
	ASSERT((LMIC.opmode & OP_NEXTCHNL)==0);
	LMIC.txend = os_getTime();
	setDrJoin(DRCHG_SET, DR_SF7);
}

static ostime_t nextJoinState (void)
{
	// Try the following:
	//	SF7/8/9/10	on a random channel 0..63
	//	SF8C		on a random channel 64..71
	//
	uint8_t failed = 0;
	if ( LMIC.datarate != DR_SF8C )
	{
		LMIC.txChnl = 64+(LMIC.txChnl&7);
		setDrJoin(DRCHG_SET, DR_SF8C);
	}
	else
	{
		LMIC.txChnl = os_getRndU1() & 0x3F;
		int8_t dr = DR_SF7 - ++LMIC.txCnt;
		if ( dr < DR_SF10 )
		{
			dr = DR_SF10;
			failed = 1; // All DR exhausted - signal failed
		}
		setDrJoin(DRCHG_SET, dr);
	}
	LMIC.opmode &= ~OP_NEXTCHNL;
	LMIC.txend = os_getTime() +
				(	isTESTMODE()		 // Avoid collision with JOIN ACCEPT being sent by GW (but we missed it - GW is still busy)
					? DNW2_SAFETY_ZONE	 // Otherwise: randomize join (street lamp case):
					// SF10:16, SF9=8,..SF8C:1secs
					: rndDelay(16 >> LMIC.datarate)
				);
	// 1 - triggers EV_JOIN_FAILED event
	return failed;
}

//
// END: US915 related stuff
//
// ================================================================================
#else
	#error Unsupported frequency band!
#endif


static void runEngineUpdate (osjob_t * osjob)
{
	engineUpdate();
}

static void reportEvent (ev_t ev)
{
	EV(devCond, INFO, (e_.reason = EV::devCond_t::LMIC_EV,
						e_.eui	= MAIN::CDEV->getEui(),
						e_.info	= ev));
	ON_LMIC_EVENT(ev);
	engineUpdate();
}

static void runReset (osjob_t * osjob)
{	// Disable session
	LMIC_reset();
	LMIC_startJoining();
	reportEvent(EV_RESET);
}

static void stateJustJoined (void)
{
	LMIC.seqnoDn	= LMIC.seqnoUp = 0;
	LMIC.rejoinCnt	= 0;
	LMIC.dnConf		= LMIC.adrChanged = LMIC.ladrAns = LMIC.devsAns = 0;
	LMIC.moreData	= LMIC.dn2Ans = LMIC.snchAns = LMIC.dutyCapAns = 0;
	LMIC.pingSetAns	= 0;
	LMIC.upRepeat	= 0;
	LMIC.adrAckReq	= LINK_CHECK_INIT;
	LMIC.dn2Dr		= DR_DNW2;
	LMIC.dn2Freq	= FREQ_DNW2;
	LMIC.bcnChnl	= CHNL_BCN;
	LMIC.ping.freq	= FREQ_PING;
	LMIC.ping.dr	= DR_PING;
}

// ================================================================================
// Decoding frames


// Decode beacon	- do not overwrite bcninfo unless we have a match!
static int decodeBeacon (void) {
	ASSERT(LMIC.dataLen == LEN_BCN); // implicit header RX guarantees this
	uint8_t * d = LMIC.frame;
	if (
#if CFG_eu868
		d[OFF_BCN_CRC1] != (uint8_t)os_crc16(d,OFF_BCN_CRC1)
#elif CFG_us915
		os_rlsbf2(&d[OFF_BCN_CRC1]) != os_crc16(d,OFF_BCN_CRC1)
#endif
		)
		return 0;	// first (common) part fails CRC check
	// First set of fields is ok
	uint32_t bcnnetid = os_rlsbf4(&d[OFF_BCN_NETID]) & 0xFFFFFF;
	if ( bcnnetid != LMIC.netid )
		return -1;	// not the beacon we're looking for

	LMIC.bcninfo.flags &= ~(BCN_PARTIAL|BCN_FULL);
	// Match - update bcninfo structure
	LMIC.bcninfo.snr	= LMIC.snr;
	LMIC.bcninfo.rssi	= LMIC.rssi;
	LMIC.bcninfo.txtime = LMIC.rxtime - AIRTIME_BCN_osticks;
	LMIC.bcninfo.time	= os_rlsbf4(&d[OFF_BCN_TIME]);
	LMIC.bcninfo.flags |= BCN_PARTIAL;

	// Check 2nd set
	if ( os_rlsbf2(&d[OFF_BCN_CRC2]) != os_crc16(d,OFF_BCN_CRC2) )
		return 1;
	// Second set of fields is ok
	LMIC.bcninfo.lat	= (int32_t)os_rlsbf4(&d[OFF_BCN_LAT-1]) >> 8; // read as signed 24-bit
	LMIC.bcninfo.lon	= (int32_t)os_rlsbf4(&d[OFF_BCN_LON-1]) >> 8; // ditto
	LMIC.bcninfo.info	= d[OFF_BCN_INFO];
	LMIC.bcninfo.flags |= BCN_FULL;
	return 2;
}


static bool decodeFrame (void) {
	uint8_t * d = LMIC.frame;
	uint8_t hdr	= d[0];
	uint8_t ftype	= hdr & HDR_FTYPE;
	int	dlen	= LMIC.dataLen;
	if ( dlen < OFF_DAT_OPTS+4 ||
		(hdr & HDR_MAJOR) != HDR_MAJOR_V1 ||
		(ftype != HDR_FTYPE_DADN	&&	ftype != HDR_FTYPE_DCDN) ) {
		// Basic sanity checks failed
		EV(specCond, WARN, (e_.reason = EV::specCond_t::UNEXPECTED_FRAME,
							e_.eui	= MAIN::CDEV->getEui(),
							e_.info	= dlen < 4 ? 0 : os_rlsbf4(&d[dlen-4]),
							e_.info2	= hdr + (dlen<<8)));
		norx:
		LMIC.dataLen = 0;
		return 0;
	}
	// Validate exact frame length
	// Note: device address was already read+evaluated in order to arrive here.
	int	fct	= d[OFF_DAT_FCT];
	uint32_t addr	= os_rlsbf4(&d[OFF_DAT_ADDR]);
	uint32_t seqno = os_rlsbf2(&d[OFF_DAT_SEQNO]);
	int	olen	= fct & FCT_OPTLEN;
	int	ackup = (fct & FCT_ACK) != 0 ? 1 : 0;	// ACK last up frame
	int	poff	= OFF_DAT_OPTS+olen;
	int	pend	= dlen-4;	// MIC

	if ( addr != LMIC.devaddr ) {
		EV(specCond, WARN, (e_.reason = EV::specCond_t::ALIEN_ADDRESS,
							e_.eui	= MAIN::CDEV->getEui(),
							e_.info	= addr,
							e_.info2	= LMIC.devaddr));
		goto norx;
	}
	if ( poff > pend ) {
		EV(specCond, ERR, (e_.reason = EV::specCond_t::CORRUPTED_FRAME,
							e_.eui	= MAIN::CDEV->getEui(),
							e_.info	= 0x1000000 + (poff-pend) + (fct<<8) + (dlen<<16)));
		goto norx;
	}

	int port = -1;
	int replayConf = 0;

	if ( pend > poff )
		port = d[poff++];

	seqno = LMIC.seqnoDn + (uint16_t)(seqno - LMIC.seqnoDn);

	if ( !aes_verifyMic(LMIC.nwkKey, LMIC.devaddr, seqno, /*dn*/1, d, pend) ) {
		EV(spe3Cond, ERR, (e_.reason = EV::spe3Cond_t::CORRUPTED_MIC,
							e_.eui1	= MAIN::CDEV->getEui(),
							e_.info1	= Base::lsbf4(&d[pend]),
							e_.info2	= seqno,
							e_.info3	= LMIC.devaddr));
		goto norx;
	}
	if ( seqno < LMIC.seqnoDn ) {
		if ( (int32_t)seqno > (int32_t)LMIC.seqnoDn ) {
			EV(specCond, INFO, (e_.reason = EV::specCond_t::DNSEQNO_ROLL_OVER,
								e_.eui	= MAIN::CDEV->getEui(),
								e_.info	= LMIC.seqnoDn, 
								e_.info2	= seqno));
			goto norx;
		}
		if ( seqno != LMIC.seqnoDn-1 || !LMIC.dnConf || ftype != HDR_FTYPE_DCDN ) {
			EV(specCond, INFO, (e_.reason = EV::specCond_t::DNSEQNO_OBSOLETE,
								e_.eui	= MAIN::CDEV->getEui(),
								e_.info	= LMIC.seqnoDn, 
								e_.info2	= seqno));
			goto norx;
		}
		// Replay of previous sequence number allowed only if
		// previous frame and repeated both requested confirmation
		replayConf = 1;
	}
	else {
		if ( seqno > LMIC.seqnoDn ) {
			EV(specCond, INFO, (e_.reason = EV::specCond_t::DNSEQNO_SKIP,
								e_.eui	= MAIN::CDEV->getEui(),
								e_.info	= LMIC.seqnoDn, 
								e_.info2	= seqno));
		}
		LMIC.seqnoDn = seqno+1;	// next number to be expected
		DO_DEVDB(LMIC.seqnoDn,seqnoDn);
		// DN frame requested confirmation - provide ACK once with next UP frame
		LMIC.dnConf = (ftype == HDR_FTYPE_DCDN ? FCT_ACK : 0);
	}

	if ( LMIC.dnConf || (fct & FCT_MORE) )
		LMIC.opmode |= OP_POLL;

	// We heard from network
	LMIC.adrChanged = LMIC.rejoinCnt = 0;
	if ( LMIC.adrAckReq != LINK_CHECK_OFF )
		LMIC.adrAckReq = LINK_CHECK_INIT;

	// Process OPTS
	int m = LMIC.rssi - RSSI_OFF - getSensitivity(LMIC.rps);
	LMIC.margin = m < 0 ? 0 : m > 254 ? 254 : m;

	uint8_t * opts = &d[OFF_DAT_OPTS];
	int oidx = 0;
	while ( oidx < olen ) {
		switch ( opts[oidx] ) {
		case MCMD_LCHK_ANS: {
			//int gwmargin = opts[oidx+1];
			//int ngws = opts[oidx+2];
			oidx += 3;
			continue;
		}
		case MCMD_LADR_REQ: {
			uint8_t p1	 = opts[oidx+1];			// txpow + DR
			uint16_t chmap	= os_rlsbf2(&opts[oidx+2]);// list of enabled channels
			uint8_t chpage = opts[oidx+4] & MCMD_LADR_CHPAGE_MASK;	 // channel page
			uint8_t uprpt	= opts[oidx+4] & MCMD_LADR_REPEAT_MASK;	 // up repeat count
			oidx += 5;

			LMIC.ladrAns = 0x80 |	 // Include an answer into next frame up
				MCMD_LADR_ANS_POWACK | MCMD_LADR_ANS_CHACK | MCMD_LADR_ANS_DRACK;
			if ( !mapChannels(chpage, chmap) )
				LMIC.ladrAns &= ~MCMD_LADR_ANS_CHACK;
			uint8_t dr = (uint8_t)(p1>>MCMD_LADR_DR_SHIFT);
			if ( !validDR(dr) ) {
				LMIC.ladrAns &= ~MCMD_LADR_ANS_DRACK;
				EV(specCond, ERR, (e_.reason = EV::specCond_t::BAD_MAC_CMD,
									e_.eui	= MAIN::CDEV->getEui(),
									e_.info	= Base::lsbf4(&d[pend]),
									e_.info2	= Base::msbf4(&opts[oidx-4])));
			}
			if ( (LMIC.ladrAns & 0x7F) == (MCMD_LADR_ANS_POWACK | MCMD_LADR_ANS_CHACK | MCMD_LADR_ANS_DRACK) ) {
				// Nothing went wrong - use settings
				LMIC.upRepeat = uprpt;
				setDrTxpow(DRCHG_NWKCMD, dr, pow2dBm(p1));
			}
			LMIC.adrChanged = 1;	// Trigger an ACK to NWK
			continue;
		}
		case MCMD_DEVS_REQ: {
			LMIC.devsAns = 1;
			oidx += 1;
			continue;
		}
		case MCMD_DN2P_SET: {
			uint8_t dr = (uint8_t)(opts[oidx+1] & 0x0F);
			uint32_t freq = convFreq(&opts[oidx+2]);
			oidx += 5;
			LMIC.dn2Ans = 0x80;	// answer pending
			if ( validDR(dr) )
				LMIC.dn2Ans |= MCMD_DN2P_ANS_DRACK;
			if ( freq != 0 )
				LMIC.dn2Ans |= MCMD_DN2P_ANS_CHACK;
			if ( LMIC.dn2Ans == (0x80|MCMD_DN2P_ANS_DRACK|MCMD_DN2P_ANS_CHACK) ) {
				LMIC.dn2Dr = dr;
				LMIC.dn2Freq = freq;
				DO_DEVDB(LMIC.dn2Dr,dn2Dr);
				DO_DEVDB(LMIC.dn2Freq,dn2Freq);
			}
			continue;
		}
		case MCMD_DCAP_REQ: {
			uint8_t cap = opts[oidx+1];
			oidx += 2;
			// A value cap=0xFF means device is OFF unless enabled again manually.
			if ( cap==0xFF )
				LMIC.opmode |= OP_SHUTDOWN;	// stop any sending
			LMIC.globalDutyRate	= cap & 0xF;
			LMIC.globalDutyAvail = os_getTime();
			DO_DEVDB(cap,dutyCap);
			LMIC.dutyCapAns = 1;
			continue;
		}
		case MCMD_SNCH_REQ: {
			uint8_t chidx = opts[oidx+1];	// channel
			uint32_t freq	= convFreq(&opts[oidx+2]); // freq
			uint8_t drs	= opts[oidx+5];	// datarate span
			LMIC.snchAns = 0x80;
			if ( freq != 0 && LMIC_setupChannel(chidx, freq, DR_RANGE_MAP(drs&0xF,drs>>4), -1) )
				LMIC.snchAns |= MCMD_SNCH_ANS_DRACK|MCMD_SNCH_ANS_FQACK;
			oidx += 6;
			continue;
		}
		case MCMD_PING_SET: {
			uint32_t freq = convFreq(&opts[oidx+1]);
			oidx += 4;
			uint8_t flags = 0x80;
			if ( freq != 0 ) {
				flags |= MCMD_PING_ANS_FQACK;
				LMIC.ping.freq = freq;
				DO_DEVDB(LMIC.ping.intvExp, pingIntvExp);
				DO_DEVDB(LMIC.ping.freq, pingFreq);
				DO_DEVDB(LMIC.ping.dr, pingDr);
			}
			LMIC.pingSetAns = flags;
			continue;
		}
		case MCMD_BCNI_ANS: {
			// Ignore if tracking already enabled
			if ( (LMIC.opmode & OP_TRACK) == 0 ) {
				LMIC.bcnChnl = opts[oidx+3];
				// Enable tracking - bcninfoTries
				LMIC.opmode |= OP_TRACK;
				// Cleared later in txComplete handling - triggers EV_BEACON_FOUND
				ASSERT(LMIC.bcninfoTries!=0);
				// Setup RX parameters
				LMIC.bcninfo.txtime = (LMIC.rxtime
										+ ms2osticks(os_rlsbf2(&opts[oidx+1]) * MCMD_BCNI_TUNIT)
										+ ms2osticksCeil(MCMD_BCNI_TUNIT/2)
										- BCN_INTV_osticks);
				LMIC.bcninfo.flags = 0;	// txtime above cannot be used as reference (BCN_PARTIAL|BCN_FULL cleared)
				calcBcnRxWindowFromMillis(MCMD_BCNI_TUNIT,1);	// error of +/-N ms 

				EV(lostFrame, INFO, (e_.reason	= EV::lostFrame_t::MCMD_BCNI_ANS,
									 e_.eui	 = MAIN::CDEV->getEui(),
									 e_.lostmic = Base::lsbf4(&d[pend]),
									 e_.info	= (LMIC.missedBcns |
													(osticks2us(LMIC.bcninfo.txtime + BCN_INTV_osticks
																- LMIC.bcnRxtime) << 8)),
									 e_.time	= MAIN::CDEV->ostime2ustime(LMIC.bcninfo.txtime + BCN_INTV_osticks)));
			}
			oidx += 4;
			continue;
		}
		}
		EV(specCond, ERR, (e_.reason = EV::specCond_t::BAD_MAC_CMD,
							e_.eui	= MAIN::CDEV->getEui(),
							e_.info	= Base::lsbf4(&d[pend]),
							e_.info2	= Base::msbf4(&opts[oidx])));
		break;
	}
	if ( oidx != olen ) {
		EV(specCond, ERR, (e_.reason = EV::specCond_t::CORRUPTED_FRAME,
							e_.eui	= MAIN::CDEV->getEui(),
							e_.info	= 0x1000000 + (oidx) + (olen<<8)));
	}

	if ( !replayConf ) {
		// Handle payload only if not a replay
		// Decrypt payload - if any
		if ( port >= 0	&&	pend-poff > 0 )
			aes_cipher(port <= 0 ? LMIC.nwkKey : LMIC.artKey, LMIC.devaddr, seqno, /*dn*/1, d+poff, pend-poff);

		EV(dfinfo, DEBUG, (e_.deveui	= MAIN::CDEV->getEui(),
							e_.devaddr = LMIC.devaddr,
							e_.seqno	= seqno,
							e_.flags	= (port < 0 ? EV::dfinfo_t::NOPORT : 0) | EV::dfinfo_t::DN,
							e_.mic	 = Base::lsbf4(&d[pend]),
							e_.hdr	 = d[LORA::OFF_DAT_HDR],
							e_.fct	 = d[LORA::OFF_DAT_FCT],
							e_.port	= port,
							e_.plen	= dlen,
							e_.opts.length = olen,
							memcpy(&e_.opts[0], opts, olen)));
	} else {
		EV(specCond, INFO, (e_.reason = EV::specCond_t::DNSEQNO_REPLAY,
							e_.eui	= MAIN::CDEV->getEui(),
							e_.info	= Base::lsbf4(&d[pend]),
							e_.info2	= seqno));
	}

	if ( // NWK acks but we don't have a frame pending
		(ackup && LMIC.txCnt == 0) ||
		// We sent up confirmed and we got a response in DNW1/DNW2
		// BUT it did not carry an ACK - this should never happen
		// Do not resend and assume frame was not ACKed.
		(!ackup && LMIC.txCnt != 0) ) {
		EV(specCond, ERR, (e_.reason = EV::specCond_t::SPURIOUS_ACK,
							e_.eui	= MAIN::CDEV->getEui(),
							e_.info	= seqno,
							e_.info2	= ackup));
	}

	if ( LMIC.txCnt != 0 ) // we requested an ACK
		LMIC.txrxFlags |= ackup ? TXRX_ACK : TXRX_NACK;

	if ( port < 0 ) {
		LMIC.txrxFlags |= TXRX_NOPORT;
		LMIC.dataBeg = poff;
		LMIC.dataLen = 0;
	} else {
		LMIC.txrxFlags |= TXRX_PORT;
		LMIC.dataBeg = poff;
		LMIC.dataLen = pend-poff;
	}
	return 1;
}


// ================================================================================
// TX/RX transaction support


static void setupRx2 (void) {
	LMIC.txrxFlags = TXRX_DNW2;
	LMIC.rps = dndr2rps(LMIC.dn2Dr);
	LMIC.freq = LMIC.dn2Freq;
	LMIC.dataLen = 0;
	os_radio(RADIO_RX);
}


static void schedRx2 (ostime_t delay, osjobcb_t func)
{
	// Add 1.5 symbols we need 5 out of 8. Try to sync 1.5 symbols into the preamble.
	LMIC.rxtime = LMIC.txend + delay + (PAMBL_SYMS - MINRX_SYMS) * dr2hsym(LMIC.dn2Dr);
	os_setTimedCallback(&LMIC.osjob, LMIC.rxtime - RX_RAMPUP, func);
}

static void setupRx1 (osjobcb_t func)
{
	LMIC.txrxFlags = TXRX_DNW1;
	// Turn LMIC.rps from TX over to RX
	LMIC.rps = setNocrc(LMIC.rps,1);
	LMIC.dataLen = 0;
	LMIC.osjob.func = func;
	os_radio(RADIO_RX);
}

// Called by HAL once TX complete and delivers exact end of TX time stamp in LMIC.rxtime
static void txDone (ostime_t delay, osjobcb_t func)
{
	if ( (LMIC.opmode & (OP_TRACK | OP_PINGABLE | OP_PINGINI)) == (OP_TRACK | OP_PINGABLE) )
	{
		rxschedInit(&LMIC.ping);	// note: reuses LMIC.frame buffer!
		LMIC.opmode |= OP_PINGINI;
	}
	// Change RX frequency / rps (US only) before we increment txChnl
	setRx1Params();
	// LMIC.rxsyms carries the TX datarate (can be != LMIC.datarate [confirm retries etc.])
	// Setup receive - LMIC.rxtime is preloaded with 1.5 symbols offset to tune
	// into the middle of the 8 symbols preamble.
#if defined(CFG_eu868)
	if ( /* TX datarate */LMIC.rxsyms == DR_FSK )
	{
		LMIC.rxtime = LMIC.txend + delay - PRERX_FSK*us2osticksRound(160);
		LMIC.rxsyms = RXLEN_FSK;
	}
	else
#endif
	{
		LMIC.rxtime = LMIC.txend + delay + (PAMBL_SYMS - MINRX_SYMS) * dr2hsym(LMIC.dndr);
		LMIC.rxsyms = MINRX_SYMS;
	}
	os_setTimedCallback(&LMIC.osjob, LMIC.rxtime - RX_RAMPUP, func);
}

// ======================================== Join frames

static void onJoinFailed (osjob_t * osjob)
{
	// Notify app - must call LMIC_reset() to stop joining
	// otherwise join procedure continues.
	reportEvent(EV_JOIN_FAILED);
}

static bool processJoinAccept (void)
{
	ASSERT(LMIC.txrxFlags != TXRX_DNW1 || LMIC.dataLen != 0);
	ASSERT((LMIC.opmode & OP_TXRXPEND) != 0);

	if ( LMIC.dataLen == 0 )
	{
	nojoinframe:
		if ( (LMIC.opmode & OP_JOINING) == 0 )
		{
			ASSERT((LMIC.opmode & OP_REJOIN) != 0);
			// REJOIN attempt for roaming
			LMIC.opmode &= ~(OP_REJOIN | OP_TXRXPEND);
			if ( LMIC.rejoinCnt < 10 )
				LMIC.rejoinCnt++;
			reportEvent(EV_REJOIN_FAILED);
			return 1;
		}
		LMIC.opmode &= ~OP_TXRXPEND;
		ostime_t delay = nextJoinState();

		EV(devCond, DEBUG, (e_.reason = EV::devCond_t::NO_JACC,
							e_.eui	= MAIN::CDEV->getEui(),
							e_.info	= LMIC.datarate|DR_PAGE,
							e_.info2	= osticks2ms(delay)));
		// Build next JOIN REQUEST with next engineUpdate call
		// Optionally, report join failed.
		// Both after a random/chosen amount of ticks.
		os_setTimedCallback(&LMIC.osjob,
							os_getTime() + delay,
							(delay & 1) != 0
							? FUNC_ADDR(onJoinFailed)		// one JOIN iteration done and failed
							: FUNC_ADDR(runEngineUpdate));	// next step to be delayed
		return 1;
	}
	uint8_t hdr	= LMIC.frame[0];
	uint8_t dlen = LMIC.dataLen;
	uint32_t mic = os_rlsbf4(&LMIC.frame[dlen - 4]); // safe before modified by encrypt!
	if ( (dlen != LEN_JA && dlen != LEN_JAEXT)
	|| (hdr & (HDR_FTYPE|HDR_MAJOR)) != (HDR_FTYPE_JACC|HDR_MAJOR_V1)
		)
	{
		EV(specCond, ERR, (	e_.reason = EV::specCond_t::UNEXPECTED_FRAME,
							e_.eui	= MAIN::CDEV->getEui(),
							e_.info	= dlen < 4 ? 0 : mic,
							e_.info2	= hdr + (dlen<<8)));
	badframe:
		if ( (LMIC.txrxFlags & TXRX_DNW1) != 0 )
			return 0;
		goto nojoinframe;
	}
	aes_encrypt(LMIC.frame + 1, dlen - 1);
	if ( !aes_verifyMic0(LMIC.frame, dlen-4) )
	{
		EV(specCond, ERR, (	e_.reason = EV::specCond_t::JOIN_BAD_MIC,
							e_.info	= mic));
		goto badframe;
	}

	uint32_t addr = os_rlsbf4(LMIC.frame + OFF_JA_DEVADDR);
	LMIC.devaddr = addr;
	LMIC.netid = os_rlsbf4(&LMIC.frame[OFF_JA_NETID]) & 0xFFFFFF;

#if defined(CFG_eu868)
	initDefaultChannels(0);
#endif
	if ( dlen > LEN_JA )
	{
#if defined(CFG_us915)
		goto badframe;
#endif
		dlen = OFF_CFLIST;
		for ( uint8_t chidx=3; chidx<8; chidx++, dlen+=3 )
		{
			uint32_t freq = convFreq(&LMIC.frame[dlen]);
			if ( freq )
				LMIC_setupChannel(chidx, freq, 0, -1);
		}
	}

	// already incremented when JOIN REQ got sent off
	aes_sessKeys(LMIC.devNonce - 1, &LMIC.frame[OFF_JA_ARTNONCE], LMIC.nwkKey, LMIC.artKey);
	DO_DEVDB(LMIC.netid,	netid);
	DO_DEVDB(LMIC.devaddr,	devaddr);
	DO_DEVDB(LMIC.nwkKey,	nwkkey);
	DO_DEVDB(LMIC.artKey,	artkey);

	EV(joininfo, INFO, (e_.arteui	= MAIN::CDEV->getArtEui(),
						e_.deveui	= MAIN::CDEV->getEui(),
						e_.devaddr = LMIC.devaddr,
						e_.oldaddr = oldaddr,
						e_.nonce	= LMIC.devNonce-1,
						e_.mic	 = mic,
						e_.reason	= ((LMIC.opmode & OP_REJOIN) != 0
										? EV::joininfo_t::REJOIN_ACCEPT
										: EV::joininfo_t::ACCEPT)));

	ASSERT((LMIC.opmode & (OP_JOINING|OP_REJOIN))!=0);
	if ( (LMIC.opmode & OP_REJOIN) != 0 )
	{	// Lower DR every try below current UP DR
		LMIC.datarate = lowerDR(LMIC.datarate, LMIC.rejoinCnt);
	}
	LMIC.opmode &= ~(OP_JOINING | OP_TRACK | OP_REJOIN | OP_TXRXPEND | OP_PINGINI) | OP_NEXTCHNL;
	stateJustJoined();
	reportEvent(EV_JOINED);
	return 1;
}

static void processRx2Jacc (osjob_t * osjob)
{
	if ( LMIC.dataLen == 0 )
		LMIC.txrxFlags = 0;	// nothing in 1st/2nd DN slot
	processJoinAccept();
}

static void setupRx2Jacc (osjob_t * osjob)
{
	LMIC.osjob.func = FUNC_ADDR(processRx2Jacc);
	setupRx2();
}

static void processRx1Jacc (osjob_t * osjob)
{
	if ( LMIC.dataLen == 0 || !processJoinAccept() )
		schedRx2(DELAY_JACC2_osticks, FUNC_ADDR(setupRx2Jacc));
}

static void setupRx1Jacc (osjob_t * osjob)
{
	setupRx1(FUNC_ADDR(processRx1Jacc));
}

static void jreqDone (osjob_t * osjob)
{
	txDone(DELAY_JACC1_osticks, FUNC_ADDR(setupRx1Jacc));
}

// ======================================== Data frames

// Fwd decl.
static bool processDnData(void);

static void processRx2DnDataDelay (osjob_t * osjob)
{
	processDnData();
}

static void processRx2DnData (osjob_t * osjob)
{
	if ( LMIC.dataLen == 0 )
	{
		LMIC.txrxFlags = 0;	// nothing in 1st/2nd DN slot
		// Delay callback processing to avoid up TX while gateway is txing our missed frame! 
		// Since DNW2 uses SF12 by default we wait 3 secs.
		os_setTimedCallback(&LMIC.osjob,
							(os_getTime() + DNW2_SAFETY_ZONE + rndDelay(2)),
							processRx2DnDataDelay);
		return;
	}
	processDnData();
}

static void setupRx2DnData (osjob_t * osjob)
{
	LMIC.osjob.func = FUNC_ADDR(processRx2DnData);
	setupRx2();
}

static void processRx1DnData (osjob_t * osjob)
{
	if ( LMIC.dataLen == 0 || !processDnData() )
		schedRx2(DELAY_DNW2_osticks, FUNC_ADDR(setupRx2DnData));
}

static void setupRx1DnData (osjob_t * osjob)
{
	setupRx1(FUNC_ADDR(processRx1DnData));
}

static void updataDone (osjob_t * osjob)
{
	txDone(DELAY_DNW1_osticks, FUNC_ADDR(setupRx1DnData));
}

// ======================================== 

static void buildDataFrame (void)
{
	bool txdata = ((LMIC.opmode & (OP_TXDATA|OP_POLL)) != OP_POLL);
	uint8_t dlen = txdata ? LMIC.pendTxLen : 0;

	// Piggyback MAC options
	// Prioritize by importance
	int	end = OFF_DAT_OPTS;
	if ( (LMIC.opmode & (OP_TRACK|OP_PINGABLE)) == (OP_TRACK|OP_PINGABLE) )
	{
		// Indicate pingability in every UP frame
		LMIC.frame[end] = MCMD_PING_IND;
		LMIC.frame[end+1] = LMIC.ping.dr | (LMIC.ping.intvExp<<4);
		end += 2;
	}
	if ( LMIC.dutyCapAns )
	{
		LMIC.frame[end] = MCMD_DCAP_ANS;
		end += 1;
		LMIC.dutyCapAns = 0;
	}
	if ( LMIC.dn2Ans )
	{
		LMIC.frame[end+0] = MCMD_DN2P_ANS;
		LMIC.frame[end+1] = LMIC.dn2Ans & ~MCMD_DN2P_ANS_RFU;
		end += 2;
		LMIC.dn2Ans = 0;
	}
	if ( LMIC.devsAns )
	{	// answer to device status
		LMIC.frame[end+0] = MCMD_DEVS_ANS;
		LMIC.frame[end+1] = LMIC.margin;
		LMIC.frame[end+2] = os_getBattLevel();
		end += 3;
		LMIC.devsAns = 0;
	}
	if ( LMIC.ladrAns )
	{	// answer to ADR change
		LMIC.frame[end+0] = MCMD_LADR_ANS;
		LMIC.frame[end+1] = LMIC.ladrAns & ~MCMD_LADR_ANS_RFU;
		end += 2;
		LMIC.ladrAns = 0;
	}
	if ( LMIC.bcninfoTries > 0 )
	{
		LMIC.frame[end] = MCMD_BCNI_REQ;
		end += 1;
	}
	if ( LMIC.adrChanged )
	{
		if ( LMIC.adrAckReq < 0 )
			LMIC.adrAckReq = 0;
		LMIC.adrChanged = 0;
	}
	if ( LMIC.pingSetAns != 0 )
	{
		LMIC.frame[end+0] = MCMD_PING_ANS;
		LMIC.frame[end+1] = LMIC.pingSetAns & ~MCMD_PING_ANS_RFU;
		end += 2;
		LMIC.pingSetAns = 0;
	}
	if ( LMIC.snchAns )
	{
		LMIC.frame[end+0] = MCMD_SNCH_ANS;
		LMIC.frame[end+1] = LMIC.snchAns & ~MCMD_SNCH_ANS_RFU;
		end += 2;
		LMIC.snchAns = 0;
	}
	ASSERT(end <= OFF_DAT_OPTS+16);

	uint8_t flen = end + (txdata ? 5+dlen : 4);
	if ( flen > MAX_LEN_FRAME )
	{
		// Options and payload too big - delay payload
		txdata = 0;
		flen = end+4;
	}
	LMIC.frame[OFF_DAT_HDR] = HDR_FTYPE_DAUP | HDR_MAJOR_V1;
	LMIC.frame[OFF_DAT_FCT] = (LMIC.dnConf
								| LMIC.adrEnabled
								| (LMIC.adrAckReq >= 0 ? FCT_ADRARQ : 0)
								| (end - OFF_DAT_OPTS));
	os_wlsbf4(LMIC.frame+OFF_DAT_ADDR,	LMIC.devaddr);

	if ( LMIC.txCnt == 0 )
	{
		LMIC.seqnoUp += 1;
		DO_DEVDB(LMIC.seqnoUp,seqnoUp);
	}
	else
	{
		EV(devCond, INFO, (e_.reason = EV::devCond_t::RE_TX,
							e_.eui	= MAIN::CDEV->getEui(),
							e_.info	= LMIC.seqnoUp-1,
							e_.info2	= ((LMIC.txCnt+1)
										| (DRADJUST[LMIC.txCnt+1] << 8)
										| ((LMIC.datarate|DR_PAGE)<<16))
						)
		);
	}
	os_wlsbf2(LMIC.frame+OFF_DAT_SEQNO, LMIC.seqnoUp - 1);

	// Clear pending DN confirmation
	LMIC.dnConf = 0;

	if ( txdata )
	{
		if ( LMIC.pendTxConf )
		{
			// Confirmed only makes sense if we have a payload (or at least a port)
			LMIC.frame[OFF_DAT_HDR] = HDR_FTYPE_DCUP | HDR_MAJOR_V1;
			if ( LMIC.txCnt == 0 ) LMIC.txCnt = 1;
		}
		LMIC.frame[end] = LMIC.pendTxPort;
		os_copyMem(LMIC.frame+end+1, LMIC.pendTxData, dlen);
		aes_cipher(LMIC.pendTxPort == 0 ? LMIC.nwkKey : LMIC.artKey,
					LMIC.devaddr, LMIC.seqnoUp - 1,
					/*up*/0, LMIC.frame + end + 1, dlen);
	}
	aes_appendMic(LMIC.nwkKey, LMIC.devaddr, LMIC.seqnoUp - 1, /*up*/0, LMIC.frame, flen - 4);

	EV(dfinfo, DEBUG, (e_.deveui	= MAIN::CDEV->getEui(),
						e_.devaddr = LMIC.devaddr,
						e_.seqno	= LMIC.seqnoUp-1,
						e_.flags	= (LMIC.pendTxPort < 0 ? EV::dfinfo_t::NOPORT : EV::dfinfo_t::NOP),
						e_.mic	 = Base::lsbf4(&LMIC.frame[flen-4]),
						e_.hdr	 = LMIC.frame[LORA::OFF_DAT_HDR],
						e_.fct	 = LMIC.frame[LORA::OFF_DAT_FCT],
						e_.port	= LMIC.pendTxPort,
						e_.plen	= txdata ? dlen : 0,
						e_.opts.length = end-LORA::OFF_DAT_OPTS,
						memcpy(&e_.opts[0], LMIC.frame+LORA::OFF_DAT_OPTS, end-LORA::OFF_DAT_OPTS)));
	LMIC.dataLen = flen;
}

// Callback from HAL during scan mode or when job timer expires.
static void onBcnRx (osjob_t * job)
{
	// If we arrive via job timer make sure to put radio to rest.
	os_radio(RADIO_RST);
	os_clearCallback(&LMIC.osjob);
	if ( LMIC.dataLen == 0 )
	{
		// Nothing received - timeout
		LMIC.opmode &= ~(OP_SCAN | OP_TRACK);
		reportEvent(EV_SCAN_TIMEOUT);
		return;
	}
	if ( decodeBeacon() <= 0 )
	{
		// Something is wrong with the beacon - continue scan
		LMIC.dataLen = 0;
		os_radio(RADIO_RXON);
		os_setTimedCallback(&LMIC.osjob, LMIC.bcninfo.txtime, FUNC_ADDR(onBcnRx));
		return;
	}
	// Found our 1st beacon
	// We don't have a previous beacon to calc some drift - assume
	// an max error of 13ms = 128sec*100ppm which is roughly +/-100ppm
	calcBcnRxWindowFromMillis(13,1);
	LMIC.opmode &= ~OP_SCAN;			// turn SCAN off
	LMIC.opmode |=	OP_TRACK;		 // auto enable tracking
	reportEvent(EV_BEACON_FOUND);	// can be disabled in callback
}

// Enable receiver to listen to incoming beacons
// netid defines when scan stops (any or specific beacon)
// This mode ends with events: EV_SCAN_TIMEOUT/EV_SCAN_BEACON
// Implicitely cancels any pending TX/RX transaction.
// Also cancels an onpoing joining procedure.
static void startScan (void)
{
	ASSERT(LMIC.devaddr!=0 && (LMIC.opmode & OP_JOINING) == 0);
	if ( (LMIC.opmode & OP_SHUTDOWN) != 0 )
		return;
	// Cancel onging TX/RX transaction
	LMIC.txCnt = LMIC.dnConf = LMIC.bcninfo.flags = 0;
	LMIC.opmode = (LMIC.opmode | OP_SCAN) & ~(OP_TXRXPEND);
	setBcnRxParams();
	LMIC.rxtime = LMIC.bcninfo.txtime = os_getTime() + sec2osticks(BCN_INTV_sec+1);
	os_setTimedCallback(&LMIC.osjob, LMIC.rxtime, FUNC_ADDR(onBcnRx));
	os_radio(RADIO_RXON);
}

bool LMIC_enableTracking (uint8_t tryBcnInfo)
{
	if ( (LMIC.opmode & (OP_SCAN|OP_TRACK|OP_SHUTDOWN)) != 0 )
		return 0;	// already in progress or failed to enable
	// If BCN info requested from NWK then app has to take are
	// of sending data up so that MCMD_BCNI_REQ can be attached.
	if ( (LMIC.bcninfoTries = tryBcnInfo) == 0 )
		startScan();
	return 1;	// enabled
}

void LMIC_disableTracking (void)
{
	LMIC.opmode &= ~(OP_SCAN|OP_TRACK);
	LMIC.bcninfoTries = 0;
	engineUpdate();
}

// ================================================================================
//
// Join stuff
//
// ================================================================================

static void buildJoinRequest (uint8_t ftype)
{
	// Do not use pendTxData since we might have a pending
	// user level frame in there. Use RX holding area instead.
	uint8_t * d = LMIC.frame;
	d[OFF_JR_HDR] = ftype;
	os_getArtEui(d + OFF_JR_ARTEUI);
	os_getDevEui(d + OFF_JR_DEVEUI);
	os_wlsbf2(d + OFF_JR_DEVNONCE, LMIC.devNonce);
	aes_appendMic0(d, OFF_JR_MIC);

	EV(joininfo,INFO,(e_.deveui	= MAIN::CDEV->getEui(),
						e_.arteui	= MAIN::CDEV->getArtEui(),
						e_.nonce	= LMIC.devNonce,
						e_.oldaddr = LMIC.devaddr,
						e_.mic	 = Base::lsbf4(&d[LORA::OFF_JR_MIC]),
						e_.reason	= ((LMIC.opmode & OP_REJOIN) != 0
									? EV::joininfo_t::REJOIN_REQUEST
									: EV::joininfo_t::REQUEST)));
	LMIC.dataLen = LEN_JR;
	LMIC.devNonce++;
	DO_DEVDB(LMIC.devNonce,devNonce);
}

static void startJoining (osjob_t * osjob)
{
	reportEvent(EV_JOINING);
}

// Start join procedure if not already joined.
bool LMIC_startJoining (void)
{
	if ( LMIC.devaddr == 0 )
	{
		// There should be no TX/RX going on
		ASSERT((LMIC.opmode & (OP_POLL|OP_TXRXPEND)) == 0);
		// Lift any previous duty limitation
		LMIC.globalDutyRate = 0;
		// Cancel scanning
		LMIC.opmode &= ~(OP_SCAN|OP_REJOIN|OP_LINKDEAD|OP_NEXTCHNL);
		// Setup state
		LMIC.rejoinCnt = LMIC.txCnt = LMIC.pendTxConf = 0;
		initJoinLoop();
		LMIC.opmode |= OP_JOINING;
		// reportEvent will call engineUpdate which then starts sending JOIN REQUESTS
		os_setCallback(&LMIC.osjob, FUNC_ADDR(startJoining));
		return 1;
	}
	return 0; // already joined
}

// ================================================================================
//
//
//
// ================================================================================

static void processPingRx (osjob_t * osjob)
{
	if ( LMIC.dataLen != 0 )
	{
		LMIC.txrxFlags = TXRX_PING;
		if ( decodeFrame() )
		{
			reportEvent(EV_RXCOMPLETE);
			return;
		}
	}
	// Pick next ping slot
	engineUpdate();
}

static bool processDnData (void)
{
	ASSERT((LMIC.opmode & OP_TXRXPEND) != 0);

	if ( LMIC.dataLen == 0 )
	{
	norx:
		if ( LMIC.txCnt != 0 )
		{
			if ( LMIC.txCnt < TXCONF_ATTEMPTS )
			{
				LMIC.txCnt += 1;
				setDrTxpow(DRCHG_NOACK, lowerDR(LMIC.datarate, DRADJUST[LMIC.txCnt]), KEEP_TXPOW);
				// Schedule another retransmission
				txDelay(LMIC.rxtime, RETRY_PERIOD_secs);
				LMIC.opmode &= ~OP_TXRXPEND;
				engineUpdate();
				return 1;
			}
			LMIC.txrxFlags = TXRX_NACK | TXRX_NOPORT;
		}
		else
		{
			// Nothing received - implies no port
			LMIC.txrxFlags = TXRX_NOPORT;
		}
		if ( LMIC.adrAckReq != LINK_CHECK_OFF )
			LMIC.adrAckReq += 1;
		LMIC.dataBeg = LMIC.dataLen = 0;

	txcomplete:
		LMIC.opmode &= ~(OP_TXDATA | OP_TXRXPEND);
		if ( (LMIC.txrxFlags & (TXRX_DNW1 | TXRX_DNW2|TXRX_PING)) != 0 && (LMIC.opmode & OP_LINKDEAD) != 0 )
		{
			LMIC.opmode &= ~OP_LINKDEAD;
			reportEvent(EV_LINK_ALIVE);
		}
		reportEvent(EV_TXCOMPLETE);
		// If we haven't heard from NWK in a while although we asked for a sign
		// assume link is dead - notify application and keep going
		if ( LMIC.adrAckReq > LINK_CHECK_DEAD )
		{
			// We haven't heard from NWK for some time although we
			// asked for a response for some time - assume we're disconnected. Lower DR one notch.
			EV(devCond, ERR, (e_.reason = EV::devCond_t::LINK_DEAD,
								e_.eui	= MAIN::CDEV->getEui(),
								e_.info	= LMIC.adrAckReq));
			setDrTxpow(DRCHG_NOADRACK, decDR((uint8_t)LMIC.datarate), KEEP_TXPOW);
			LMIC.adrAckReq = LINK_CHECK_CONT;
			LMIC.opmode |= OP_REJOIN|OP_LINKDEAD;
			reportEvent(EV_LINK_DEAD);
		}
		// If this falls to zero the NWK did not answer our MCMD_BCNI_REQ commands - try full scan
		if ( LMIC.bcninfoTries > 0 )
		{
			if ( (LMIC.opmode & OP_TRACK) != 0 )
			{
				reportEvent(EV_BEACON_FOUND);
				LMIC.bcninfoTries = 0;
			}
			else if ( --LMIC.bcninfoTries == 0 )
			{
				startScan();	// NWK did not answer - try scan
			}
		}
		return 1;
	}
	if ( !decodeFrame() )
	{
		if ( (LMIC.txrxFlags & TXRX_DNW1) != 0 )
			return 0;
		goto norx;
	}
	goto txcomplete;
}

static void processBeacon (osjob_t * osjob)
{
	ostime_t lasttx = LMIC.bcninfo.txtime;	// save here - decodeBeacon might overwrite
	uint8_t flags = LMIC.bcninfo.flags;
	ev_t ev;

	if ( LMIC.dataLen != 0 && decodeBeacon() >= 1 )
	{
		ev = EV_BEACON_TRACKED;
		if ( (flags & (BCN_PARTIAL|BCN_FULL)) == 0 )
		{
			// We don't have a previous beacon to calc some drift - assume
			// an max error of 13ms = 128sec*100ppm which is roughly +/-100ppm
			calcBcnRxWindowFromMillis(13,0);
			goto rev;
		}
		// We have a previous BEACON to calculate some drift
		int16_t drift = BCN_INTV_osticks - (LMIC.bcninfo.txtime - lasttx);
		if ( LMIC.missedBcns > 0 )
		{
			drift = LMIC.drift + (drift - LMIC.drift) / (LMIC.missedBcns+1);
		}
		if ( (LMIC.bcninfo.flags & BCN_NODRIFT) == 0 )
		{
			int16_t diff = LMIC.drift - drift;
			if ( diff < 0 ) diff = -diff;
			LMIC.lastDriftDiff = diff;
			if ( LMIC.maxDriftDiff < diff )
				LMIC.maxDriftDiff = diff;
			LMIC.bcninfo.flags &= ~BCN_NODDIFF;
		}
		LMIC.drift = drift;
		LMIC.missedBcns = LMIC.rejoinCnt = 0;
		LMIC.bcninfo.flags &= ~BCN_NODRIFT;
		EV(devCond,INFO,(e_.reason = EV::devCond_t::CLOCK_DRIFT,
						 e_.eui	= MAIN::CDEV->getEui(),
						 e_.info	= drift,
						 e_.info2	= /*occasion BEACON*/0));
		ASSERT((LMIC.bcninfo.flags & (BCN_PARTIAL|BCN_FULL)) != 0);
	}
	else
	{
		ev = EV_BEACON_MISSED;
		LMIC.bcninfo.txtime += BCN_INTV_osticks - LMIC.drift;
		LMIC.bcninfo.time	+= BCN_INTV_sec;
		LMIC.missedBcns++;
		// Delay any possible TX after surmised beacon - it's there although we missed it
		txDelay(LMIC.bcninfo.txtime + BCN_RESERVE_osticks, 4);
		if ( LMIC.missedBcns > MAX_MISSED_BCNS )
			LMIC.opmode |= OP_REJOIN;	// try if we can roam to another network
		if ( LMIC.bcnRxsyms > MAX_RXSYMS )
		{
			LMIC.opmode &= ~(OP_TRACK|OP_PINGABLE|OP_PINGINI|OP_REJOIN);
			reportEvent(EV_LOST_TSYNC);
			return;
		}
	}
	LMIC.bcnRxtime = LMIC.bcninfo.txtime + BCN_INTV_osticks - calcRxWindow(0,DR_BCN);
	LMIC.bcnRxsyms = LMIC.rxsyms;	
rev:
#if CFG_us915
	LMIC.bcnChnl = (LMIC.bcnChnl+1) & 7;
#endif
	if ( (LMIC.opmode & OP_PINGINI) != 0 )
		rxschedInit(&LMIC.ping);	// note: reuses LMIC.frame buffer!
	reportEvent(ev);
}

static void startRxBcn (osjob_t * osjob)
{
	LMIC.osjob.func = FUNC_ADDR(processBeacon);
	os_radio(RADIO_RX);
}

static void startRxPing (osjob_t * osjob)
{
	LMIC.osjob.func = FUNC_ADDR(processPingRx);
	os_radio(RADIO_RX);
}

// Decide what to do next for the MAC layer of a device
static void engineUpdate (void)
{
	// Check for ongoing state: scan or TX/RX transaction
	if ( (LMIC.opmode & (OP_SCAN|OP_TXRXPEND|OP_SHUTDOWN)) != 0 ) 
		return;

	if ( LMIC.devaddr == 0 && (LMIC.opmode & OP_JOINING) == 0 )
	{
		LMIC_startJoining();
		return;
	}

	ostime_t now	= os_getTime();
	ostime_t rxtime = 0;
	ostime_t txbeg	= 0;

	if ( (LMIC.opmode & OP_TRACK) != 0 )
	{
		// We are tracking a beacon
		ASSERT( now + RX_RAMPUP - LMIC.bcnRxtime <= 0 );
		rxtime = LMIC.bcnRxtime - RX_RAMPUP;
	}

	if ( (LMIC.opmode & (OP_JOINING|OP_REJOIN|OP_TXDATA|OP_POLL)) != 0 )
	{
		// Need to TX some data...
		// Assuming txChnl points to channel which first becomes available again.
		bool jacc = ((LMIC.opmode & (OP_JOINING|OP_REJOIN)) != 0 ? 1 : 0);
		// Find next suitable channel and return availability time
		if ( (LMIC.opmode & OP_NEXTCHNL) != 0 )
		{
			txbeg = LMIC.txend = nextTx(now);
			LMIC.opmode &= ~OP_NEXTCHNL;
		}
		else
		{
			txbeg = LMIC.txend;
		}
		// Delayed TX or waiting for duty cycle?
		if ( (LMIC.globalDutyRate != 0 || (LMIC.opmode & OP_RNDTX) != 0)	&&	(txbeg - LMIC.globalDutyAvail) < 0 )
			txbeg = LMIC.globalDutyAvail;
		// If we're tracking a beacon...
		// then make sure TX-RX transaction is complete before beacon
		if ((LMIC.opmode & OP_TRACK) != 0
		&&	txbeg + (jacc ? JOIN_GUARD_osticks : TXRX_GUARD_osticks) - rxtime > 0 )
		{
			// Not enough time to complete TX-RX before beacon - postpone after beacon.
			// In order to avoid clustering of postponed TX right after beacon randomize start!
			txDelay(rxtime + BCN_RESERVE_osticks, 16);
			txbeg = 0;
			goto checkrx;
		}
		// Earliest possible time vs overhead to setup radio
		if ( txbeg - (now + TX_RAMPUP) < 0 )
		{
			// We could send right now!
			txbeg = now;
			uint8_t txdr = (uint8_t)LMIC.datarate;
			if ( jacc )
			{
				uint8_t ftype;
				if ( (LMIC.opmode & OP_REJOIN) != 0 )
				{
					txdr = lowerDR(txdr, LMIC.rejoinCnt);
					ftype = HDR_FTYPE_REJOIN;
				}
				else
					ftype = HDR_FTYPE_JREQ;

				buildJoinRequest(ftype);
				LMIC.osjob.func = FUNC_ADDR(jreqDone);
			}
			else
			{
				if ( LMIC.seqnoDn >= 0xFFFFFF80 )
				{
					// Imminent roll over - proactively reset MAC
					EV(specCond, INFO, (e_.reason = EV::specCond_t::DNSEQNO_ROLL_OVER,
										e_.eui	= MAIN::CDEV->getEui(),
										e_.info	= LMIC.seqnoDn, 
										e_.info2	= 0));
					// Device has to react! NWK will not roll over and just stop sending.
					// Thus, we have N frames to detect a possible lock up.
				reset:
					os_setCallback(&LMIC.osjob, FUNC_ADDR(runReset));
					return;
				}
				if ( (LMIC.txCnt==0 && LMIC.seqnoUp == 0xFFFFFFFF) )
				{
					// Roll over of up seq counter
					EV(specCond, ERR, (e_.reason = EV::specCond_t::UPSEQNO_ROLL_OVER,
										e_.eui	= MAIN::CDEV->getEui(),
										e_.info2	= LMIC.seqnoUp));
					// Do not run RESET event callback from here!
					// App code might do some stuff after send unaware of RESET.
					goto reset;
				}
				buildDataFrame();
				LMIC.osjob.func = FUNC_ADDR(updataDone);
			}
			LMIC.rps	= setCr(updr2rps(txdr), (uint8_t)LMIC.errcr);
			LMIC.dndr	= txdr;	// carry TX datarate (can be != LMIC.datarate) over to txDone/setupRx1
			LMIC.opmode = (LMIC.opmode & ~(OP_POLL | OP_RNDTX)) | OP_TXRXPEND | OP_NEXTCHNL;
			updateTx(txbeg);
			os_radio(RADIO_TX);
			return;
		}
		// Cannot yet TX
		if ( (LMIC.opmode & OP_TRACK) == 0 )
			goto txdelay; // We don't track the beacon - nothing else to do - so wait for the time to TX
		// Consider RX tasks
		if ( txbeg == 0 ) // zero indicates no TX pending
			txbeg += 1;	// TX delayed by one tick (insignificant amount of time)
	}
	else
	{
		// No TX pending - no scheduled RX
		if ( (LMIC.opmode & OP_TRACK) == 0 )
			return;
	}

	// Are we pingable?
checkrx:
	if ( (LMIC.opmode & OP_PINGINI) != 0 )
	{
		// One more RX slot in this beacon period?
		if ( rxschedNext(&LMIC.ping, now+RX_RAMPUP) )
		{
			if ( txbeg != 0	&&	(txbeg - LMIC.ping.rxtime) < 0 )
				goto txdelay;
			LMIC.rxsyms	= LMIC.ping.rxsyms;
			LMIC.rxtime	= LMIC.ping.rxtime;
			LMIC.freq	= LMIC.ping.freq;
			LMIC.rps	 = dndr2rps(LMIC.ping.dr);
			LMIC.dataLen = 0;
			ASSERT(LMIC.rxtime - now+RX_RAMPUP >= 0 );
			os_setTimedCallback(&LMIC.osjob, LMIC.rxtime - RX_RAMPUP, FUNC_ADDR(startRxPing));
			return;
		}
		// no - just wait for the beacon
	}

	if ( txbeg != 0	&&	(txbeg - rxtime) < 0 )
		goto txdelay;

	setBcnRxParams();
	LMIC.rxsyms = LMIC.bcnRxsyms;
	LMIC.rxtime = LMIC.bcnRxtime;
	if ( now - rxtime >= 0 )
	{
		LMIC.osjob.func = FUNC_ADDR(processBeacon);
		os_radio(RADIO_RX);
		return;
	}
	os_setTimedCallback(&LMIC.osjob, rxtime, FUNC_ADDR(startRxBcn));
	return;

txdelay:
	EV(devCond, INFO, (e_.reason = EV::devCond_t::TX_DELAY,
						e_.eui	= MAIN::CDEV->getEui(),
						e_.info	= osticks2ms(txbeg-now),
						e_.info2	= LMIC.seqnoUp-1));
	os_setTimedCallback(&LMIC.osjob, txbeg-TX_RAMPUP, FUNC_ADDR(runEngineUpdate));
}

void LMIC_setAdrMode (bool enabled)
{
	LMIC.adrEnabled = enabled ? FCT_ADREN : 0;
}

//	Should we have/need an ext. API like this?
void LMIC_setDrTxpow (uint8_t dr, int8_t txpow)
{
	setDrTxpow(DRCHG_SET, dr, txpow);
}

void LMIC_shutdown (void)
{
	os_clearCallback(&LMIC.osjob);
	os_radio(RADIO_RST);
	LMIC.opmode |= OP_SHUTDOWN;
}

void LMIC_reset (void)
{
	EV(devCond, INFO, (	e_.reason = EV::devCond_t::LMIC_EV,
						e_.eui	= MAIN::CDEV->getEui(),
						e_.info	= EV_RESET));
	os_radio(RADIO_RST);
	os_clearCallback(&LMIC.osjob);

	os_clearMem((uint8_t *)&LMIC, SIZEOFEXPR(LMIC));
	LMIC.devaddr		= 0;
	LMIC.devNonce		= os_getRndU2();
	LMIC.opmode			= OP_NONE;
	LMIC.errcr			= CR_4_5;
	LMIC.adrEnabled		= FCT_ADREN;
	LMIC.dn2Dr			= DR_DNW2;		// we need this for 2nd DN window of join accept
	LMIC.dn2Freq		= FREQ_DNW2;	// ditto
	LMIC.ping.freq		= FREQ_PING;	// defaults for ping
	LMIC.ping.dr		= DR_PING;		// ditto
	LMIC.ping.intvExp	= 0xFF;

#if defined(CFG_us915)
	initDefaultChannels();
#endif

	DO_DEVDB(LMIC.devaddr,	devaddr);
	DO_DEVDB(LMIC.devNonce,	devNonce);
	DO_DEVDB(LMIC.dn2Dr,	dn2Dr);
	DO_DEVDB(LMIC.dn2Freq,	dn2Freq);
	DO_DEVDB(LMIC.ping.freq, pingFreq);
	DO_DEVDB(LMIC.ping.dr,	pingDr);
	DO_DEVDB(LMIC.ping.intvExp, pingIntvExp);
}

void LMIC_init (void)
{
	LMIC.opmode = OP_SHUTDOWN;
}

void LMIC_clrTxData (void)
{
	LMIC.opmode &= ~(OP_TXDATA | OP_TXRXPEND | OP_POLL);
	LMIC.pendTxLen = 0;
	if ( (LMIC.opmode & (OP_JOINING|OP_SCAN)) != 0 ) // do not interfere with JOINING
		return;

	os_clearCallback(&LMIC.osjob);
	os_radio(RADIO_RST);
	engineUpdate();
}

void LMIC_setTxData (void)
{
	LMIC.opmode |= OP_TXDATA;
	if ( (LMIC.opmode & OP_JOINING) == 0 )
		LMIC.txCnt = 0;			 // cancel any ongoing TX/RX retries
	engineUpdate();
}

//
int LMIC_setTxData2 (uint8_t port, uint8_t * data, uint8_t dlen, uint8_t confirmed)
{
	if ( dlen > SIZEOFEXPR(LMIC.pendTxData) )
		return -2;
	if ( data != NULL )
		os_copyMem(LMIC.pendTxData, data, dlen);

	LMIC.pendTxConf = confirmed;
	LMIC.pendTxPort = port;
	LMIC.pendTxLen	= dlen;
	LMIC_setTxData();
	return 0;
}

// Send a payload-less message to signal device is alive
void LMIC_sendAlive (void)
{
	LMIC.opmode |= OP_POLL;
	engineUpdate();
}

// Check if other networks are around.
void LMIC_tryRejoin (void)
{
	LMIC.opmode |= OP_REJOIN;
	engineUpdate();
}

//! \brief Setup given session keys
//! and put the MAC in a state as if 
//! a join request/accept would have negotiated just these keys.
//! It is crucial that the combinations `devaddr/nwkkey` and `devaddr/artkey`
//! are unique within the network identified by `netid`.
//! NOTE: on Harvard architectures when session keys are in flash:
//!	Caller has to fill in LMIC.{nwk,art}Key	before and pass {nwk,art}Key are NULL
//! \param netid a 24 bit number describing the network id this device is using
//! \param devaddr the 32 bit session address of the device. It is strongly recommended
//!	to ensure that different devices use different numbers with high probability.
//! \param nwkKey	the 16 byte network session key used for message integrity.
//!	 If NULL the caller has copied the key into `LMIC.nwkKey` before.
//! \param artKey	the 16 byte application router session key used for message confidentiality.
//!	 If NULL the caller has copied the key into `LMIC.artKey` before.
void LMIC_setSession (uint32_t netid, devaduint8_t devaddr, uint8_t * nwkKey, uint8_t * artKey)
{
	LMIC.netid = netid;
	LMIC.devaddr = devaddr;

	if ( nwkKey != NULL )
		os_copyMem(LMIC.nwkKey, nwkKey, 16);
	if ( artKey != NULL )
		os_copyMem(LMIC.artKey, artKey, 16);

#if defined(CFG_eu868)
	initDefaultChannels(0);
#endif

	LMIC.opmode &= ~(OP_JOINING | OP_TRACK | OP_REJOIN | OP_TXRXPEND | OP_PINGINI);
	LMIC.opmode |= OP_NEXTCHNL;
	stateJustJoined();

	DO_DEVDB(LMIC.netid,	netid);
	DO_DEVDB(LMIC.devaddr, devaddr);
	DO_DEVDB(LMIC.nwkKey,	nwkkey);
	DO_DEVDB(LMIC.artKey,	artkey);
	DO_DEVDB(LMIC.seqnoUp, seqnoUp);
	DO_DEVDB(LMIC.seqnoDn, seqnoDn);
}

// Enable/disable link check validation.
// LMIC sets the ADRACKREQ bit in UP frames if there were no DN frames
// for a while. It expects the network to provide a DN message to prove
// connectivity with a span of UP frames. If this no such prove is coming
// then the datarate is lowered and a LINK_DEAD event is generated.
// This mode can be disabled and no connectivity prove (ADRACKREQ) is requested
// nor is the datarate changed.
// This must be called only if a session is established (e.g. after EV_JOINED)
void LMIC_setLinkCheckMode (bool enabled)
{
	LMIC.adrChanged = 0;
	LMIC.adrAckReq = enabled ? LINK_CHECK_INIT : LINK_CHECK_OFF;
}

 
